The Effect Of Enzymolysis And Fermentation On The Volatile Compounds In The Intestines And Gonads Of Sea Cucumber Using Headspace-gas Chromatography-ion Mobility Spectroscopy(HS-GC-IMS)

Sea cucumbers are echinoderms from the class Holothuroidea.It possesses very high tonic health function and has been known as one of the ‘eight precious seafoods' from ancient times because of its extremely high nutrition,health and medical values.But so far,by-products generated during sea cucumbers processing,like sea cucumber intestine and gonads,have not been fully utilized.Thus,this work will focus on the effects of different processing methods on physico-chemical features and flavors of sea cucumber intestinal and gonads.Specific research results are as follows:(1)Preparation and process optimization of enzymatic hydrolysate of sea cucumber intestine and gonads.This part demonstrated that the optimal degree of hydrolysis under optimal conditions was 47.6%,and the distribution of small molecule peptides in the hydrolysate is 64.7%.The antioxidant properties were then assessed by in vitro tests: scavenging rate of DPPH radicals was 69.3%;ferric-reducing antioxidant power(FRAP)value was 1.614;hydroxyl radical scavenging rate was 43.5%.In addition,protein was the most changed component among the basic constituents of the hydrolysis,and that could be attributed to the fact that macromolecular protein was broken down into peptides with different molecular weights after enzymatic hydrolysis.(2)Preparation and process optimization of fermentation broth of sea cucumber intestine and gonads.In this experiment,the hydrolysate of sea cucumber intestine and gonads was used as raw material for fermentation,using pH value as index,single factor experiment and orthogonal experiment were used to optimize the fermentation process.pH,acidity,reducing sugar content and sensory indicators of fermentation broth were determination under different fermentation conditions.A complex strain was used which composed of Streptococcus thermophilus,Lactobacillus bulgaricus,Lactobacillus acidophilus and Bifidobacterium lactis.Finally,the optimal fermentation conditions were a fermentation temperature of 42 °C time,fermentation time 10 hours,lactose content 6% and strain content 0.1%.Further,the sensory score of the optimal group was 9.03,acidity value was 36 °T,protein content was 1.08%,total sugar content was 4.38%,number of lactic acid bacteria was 2000 CFU/mL,and the content of small molecular peptide in fermentation broth was 64.37%.(3)Effect of enzymatic hydrolysis and fermentation on volatile substances of sea cucumber intestinal and gonads was studied using HS-GC-IMS techniques.HS-GC-IMS was used to determine the volatile substances in the crude liquid,enzymatic hydrolysate and fermentation broth of sea cucumber intestine and gonads in order to investigate the effect and mechanism of enzyme hydrolysis and fermentation on the flavor of seafood.Results showed that enzymatic hydrolysis and fermentation had a great influence on the flavor substances on the crude liquid of sea cucumber intestine and gonads.From the 49 substances that are accurately qualitative,the main flavor substances in the crude liquid were aldehydes and ketones,such as 2-pentanone,2,3-glutaraldehyde,octanal,etc.;and similarly,the enzymatic hydrolysate also mainly contains some aldehydes and ketones,such as butyraldehyde,hexanal,thiophene,pyrazine,furan and other heterocyclic derivatives;while for the fermentation broth was mainly contained with alcohols and acids,such as propanol,acetic acid,3-methyl-3-butanenol,2-Methylbutyric acid,etc.,which was mainly alcohol flavor.Above results indicating that fermentation can significantly improve the flavor of enzymolysis of sea cucumber intestine and gonads.